An evolved universal mobile telecommunication system territorial radio access network (Evolved Universal Mobile Telecommunication System Territorial Radio Access Network; E-UTRAN) and an evolved packet core network (Evolved Packet Core Network, EPC) form an evolved packet system (Evolved Packet System, EPS). The evolved packet system generally adopts an Internet Protocol (Internet Protocol; IP) multimedia subsystem (IP Multimedia Subsystem; IMS) to provide a voice service.
Given that an initial E-UTRAN deployment cannot achieve a whole-network coverage, therefore, IMS voice cannot be provided outside an E-UTRAN coverage scope. To maintain continuity of a voice call along an E-UTRAN coverage boundary, a 3rd generation partnership (The 3rd Generation Partnership Project; 3GPP) defines a single radio voice call continuity (Single Radio Voice Call Continuity; SRVCC) technology to achieve a handover from an E-UTRAN to a circuit domain (Circuit Switching; CS) of an enhanced radio access network (GSM EDGE Radio Access Network; GERAN) or a territorial radio access network (UMTS Territorial Radio Access Network; UTRAN), or a handover from 3GPP2 1xCS packet switched (Packet Switched; PS) to the CS. Further, the SRVCC technology also achieves a handover from UTRAN high speed packet access (High Speed Packet Access, HSPA) to the GERAN/UTRAN. A radio access network network element may trigger performing an SRVCC handover only if it is learned that a user equipment (User Equipment/Mobile Station; UE/MS, hereinafter collectively referred to as a UE) and the mobility management network element (as regards different radio communication networks, it may be a mobility management entity (Mobility Management Entity; MME) or a service general packet radio technology (General Packet Radio Service; GPRS) supporting node (Serving GPRS Support Node; SGSN), and so on) support the SRVCC, and under a scenario in which a user is allowed to use the SRVCC.
When the prior art applies to an attach or a location update process, if the mobility management network element learns, by receiving an attach request/location update request message sent by the user equipment, that the UE has the SRVCC capability, learns, from subscription data sent by a home subscriber server, that the user is allowed to use the SRVCC, and learns that the mobility management network element supports the SRVCC, the mobility management network element sends an initial context setup request message to the radio access network network element, indicating that the radio access network element may perform an SRVCC operation.
However, when the prior art applies to a packet switched handover (Packet Switched Handover; PS HO) process, the target mobility management network element may not correctly learn whether the user is allowed to use the SRVCC, and accordingly the target radio access network network element may not correctly learn whether the SRVCC operation may be performed. In addition, the target radio access network network element incorrectly triggers an SRVCC handover. This results in an SRVCC handover failure and a waste of a large number of relevant exchanged signaling; or, this may result in a failure of performing the SRVCC handover and interruption of a user voice service.